1. Field of the Invention
This invention relates to two-stroke cycle engines, and more particularly, to two-stroke cycle engines having a linear gear drive in which a piston rod unit moves linearly.
2. Description of the Prior Art
A linear gear drive system is a relatively simple gear relationship which includes a fixed ring gear and a pinion gear rotating within the ring gear for converting reciprocating linear motion into a balanced rotary motion.
With linear motion of a piston rod unit, the typical piston wrist pin required for non-linear type reciprocating engines is eliminated. This allows a smaller, lighter weight piston to be assembled to a piston rod as a one-piece unit. Moreover, linear motion of a piston rod unit allows the cylinder to be sealed at its lower base and thus to be isolated from the gearcase, and in fact this allows the cylinder to itself comprise two separate chambers, an upper chamber above the piston, and a second chamber below the piston.
Operating in a two-stroke cycle mode, with linear motion of the piston rod unit, the operation and timing of the valves is simplified. The intake valve need only be a relatively simple check valve, such as a reed valve, or the like, although the mass of intake air would be greater if a mechanically operated valve is employed. Because operation is two-stroke, valve timing and the corresponding mechanical control is relatively simple.
In prior art two stroke cycle engines, exhaust valves are typically ports covered and uncovered (closed and opened) by the piston itself. The exhaust valve, in the apparatus of the present invention, is operated from the center of the piston and piston rod assembly and it seats or extends into the cylinder head.
Linear motion of a piston rod is not a new motion. Rather, it is a relatively well-known hypocycloid type curve. A hypocycloid is a curve generated by a point on a circle when the circle is rolled inside a larger circle. When the diameter of the smaller circle is equal to the radius of the larger circle, or one-half the diameter of the larger circle, the hypocycloid becomes a straight line. In actuality, every point on the smaller circle then moves in a straight line.
The same type of hypocycloid linear motion occurs when a small pinion gear is rotated inside of a fixed, internal or ring gear, with the pitch diameter of the internal gear twice that of the pinion gear. Any point on the pitch circle of the pinion moves in a straight line inside the internal gear.
U.S. Pat. No. 587,380 (Ziegler) discloses this type of linear motion in a pump using symmetrical gearing to distribute forces and to eliminate side thrust.
U.S. Pat. No. 1,056,746 (Pitts) discloses the same type of linear motion in which two pairs of counterbalances are utilized. One pair of counterbalances is on the output shaft and the other pair of counterbalances is on the pinion assembly, and inside the first pair of counterbalances.
The mechanical movement described in the '746 patent was applied to an internal combustion engine by the same inventor. The internal combustion engine matured into U.S. Pat. No. 1,090,647.
U.S. Pat. No. 1,579,083 (Collins) discloses a similar linear gear movement in an opposed piston environment. Two pistons, aligned with each other and in cylinders on opposite ends of the gear system, are connected by aligned piston rods. The one set of gears and an output shaft are supported by the frame.
U.S. Pat. No. 2,886,976 (Dean) discloses various embodiments of systems for converting motion into linear movement.
U.S. Pat. No. 3,175,544 (Hughes) discloses internal combustion engines utilizing a slider mechanism for linear movement of piston rods and multiple pistons.
U.S. Pat. No. 3,258,992 (Hittell) discloses reciprocating piston engines utilizing a slider mechanism for linear movement and double opposed cylinders and pistons. That is, on a single crankshaft are at least two sets of piston rod units and each pair of piston rod units moves in opposed cylinders. In the basic environment, four cylinders are utilized.
U.S. Pat. No. 3,277,743 (Kell) discloses two different embodiments of linear motion mechanisms. The mechanical movement, or the mechanisms involved in mechanical movement, is disclosed in the '743 patent. No particular reference to an engine, a pump, compressor, etc., is discussed.
U.S. Pat. No. 3,329,134 (Llewellyn) discloses an internal combustion engine with opposed pistons utilizing a slider mechanism for linear movement.
U.S. Pat. No. 3,563,223 (Ishida) discloses another reciprocating engine environment utilizing linear gear movement. Again, opposed pistons are utilized.
U.S. Pat. No. 3,744,342 (Kinoshita) discloses a reciprocating piston engine utilizing an internal gear and a piston and crank mechanism for balancing primary inertia forces. The internal gear, which is fixed, has twice the number of teeth as a gear which rotates with the balance weight.
U.S. Pat. No. 3,791,227 (Cherry) discloses counterweight balancing of linear movement in an engine apparatus. There is no discussion on a particular type of engine. Rather the patent discusses engines in general terms of mechanical movement.
U.S. Pat. No. 3,886,805 (Koderman) discloses a crank gear system for converting linear movement into rotary movement. The apparatus is disclosed in terms of a crank gear and planetary crankshaft system.
U.S. Pat. No. 4,078,439 (Iturriaga-Notario) discloses compressor apparatus utilizing a slider mechanism for linear movement of opposed piston and cylinder systems.
U.S. Pat. No. 4,173,151 (Grundy) discloses a slider mechanism for linear movement in an engine in which the pistons are offset from each other, as in a vee configuration. Several different embodiments are shown, utilizing different piston and cylinder arrangements, but all involving linear piston rod movement.
U.S. Pat. No. 4,237,741 (Huf et al) discloses a modified hypocycloid gear and a mechanical transmission system. Several different embodiments, including different types of internal combustion engines, are disclosed.